The present invention generally relates to a method for manufacturing a multilayer wiring board, and a wiring pattern forming apparatus. More specifically, the present invention is directed to such a method for manufacturing a multilayer wiring board and a wiring pattern forming apparatus such that when a large number of LSI mounting areas are provided on a ceramics multilayer wiring board, desirable thin-film wiring patterns are formed by being exposed in a batch mode.
As one of the current attractive LSI mounting (packing) techniques, multilayer wiring boards are utilized on which a large number of LSIs are mounted. In particular, ceramics materials with a supreme thermal (heat) conductivity are employed as board materials, and ceramics multilayer wiring boards constituted by stacking several tens of circuit wiring layers are used (e.g., see Japanese magazine "THIN-FILM HANDBOOK" issued by Ohm publishing firm on May 30, 1988).
Now, a description will be made of a method for manufacturing a ceramics multilayer wiring board.
Either oxide such as alumina powder, murite powder, and glass powder, or a mixture of carbide powder and nitride powder is mixed with an organic polymer material together with a solving agent and plasticizer to thereby form slurry.
Subsequently, after the slurry is defoamed and the viscosity coefficient thereof is adjusted under reduced pressure, the resultant slurry is processed by a sheet forming apparatus so as to have a predetermined thickness and a predetermined width, and the solving agent is vaporized by way of a drying process, so that a flexible ceramics green sheet is formed.
A through hole is formed in the formed ceramics green sheet by using a punch, or laser. Thick-film paste made of metal powder and a viscosity fluid is printed on this through hole and a surface of the ceramics green sheet by employing a printing screen having a desirable opening. A conductive material is filled into the through hole, and a circuit pattern of a conductive film is formed on the surface of the ceramics green sheet.
Several tens of sheets are stacked in accordance with the patterns of the circuit layers to be stacked.
Pressure is applied to the above-described sheet-stacked layer, and then this sheet-stacked layer is heated at temperatures from 100.degree. C. to 200.degree. C., so that the sheets are adhered to each other by utilizing thermoplasticity of the organic polymer material contained in the sheets, and thus a sheet crimp member is manufactured.
Thereafter, the sheet crimp member is further heated at high temperatures from 900.degree. C. to 1,700.degree. C. so as to vaporize the organic polymer materials for constituting the sheet material and the film pattern material, and also the solving agent. Also, the ceramics powder for constituting the sheet material, and the metal powder for constituting the film pattern are sintered to thereby constitute the ceramics multilayer wiring board.
Then, after a desirable thin-film outer wiring pattern has been formed on the surface of this ceramics multilayer wiring board, a large number of LSI chips are arranged on this board and is mounted in high density. These LSI chips are mutually connected by the multilayer wiring patterns formed inside the board, and the outer wiring patterns formed on the surface of the board.
When a thin-film wiring pattern is formed, after photoresist is coated on the multilayer wiring board, the photoresist-coated multilayer wiring board is exposed in a photomask pattern shape by utilizing a photomask having a predetermined opening portion, and then the photoresist of the exposed portion is removed to thereby form an organic insulating film. Under such a circumstance, to form the external wiring pattern in higher precision, the photomask must be correctly aligned with respect to the multilayer wiring board. In general, when this sort of alignment is carried out, through holes formed in two corners, or four corners of an outer edge of a board are used as target marks, and these target marks are aligned with target marks of a photomask.
In the ceramics sintering step, unwanted distortion or unwanted deformation will occur in the fabricated multilayer wiring board. As a consequence, in accordance with the conventional alignment method, although positional shifts of the patterns located near the alignment through holes for the board are small, positional shifts of the patterns located apart from the through holes are large. It is practically difficult to eliminate the large positional shifts.
On the other hand, this sort of problem may be avoided by employing the split exposure method, and the step exposure method. In this split exposure method, the board is split into a plurality of regions, the alignment process operations are carried out with respect to each of these split regions, and then the photomask patterns are exposed. In the step exposure method, the photomask patterns are successively exposed in a predetermined pitch. However, these conventional exposure methods own such problems that since the manufacturing steps are considerably increased, higher cost is necessarily required.